Cervical stenosis with spinal cord compression and consequent myelopathy is a very common problem encountered by the spine surgeon. The usual cause of multilevel cervical stenosis is spondylosis and/or ossification of the posterior longitudinal ligament. Surgical decompression either through an anterior or posterior approach can be undertaken.
An anterior approach usually involves multilevel corpectomy with fusion and stabilization. The main drawback of this technique is the increased time and complexity of the procedure as well as the risk of pseudoarthrosis and accelerated degeneration at the levels above and below the fusion.
A posterior approach has traditionally involved a simple laminectomy, laminectomy with facet fusion, or laminoplasty. The drawback of a simple laminectomy is the risk of late clinical deterioration from either kyphosis, instability, or post-laminectomy scar formation. Laminectomy with facet fusion decreases the risk of kyphosis but it also decreases the range of motion in the spine and increases the risk of accelerated degeneration at the levels above and below the fusion.
Laminoplasty either through open door or double door technique provides greater stability and range of motion when compared with laminectomy alone. This technique entails laminoplasty for decompression and fixation with a plate with or without laminar fusion. The principle behind laminar fixation is that it maintains the decompression following laminoplasty as well as the displaced lamina in a fixed position thereby also providing stabilization since facet motion is preserved.
U.S. patent application Ser. No. 10/035,281 by the applicant describes several laminar fixation plates with and without a bone spacer that allow for lamina fixation and fusion. U.S. Pat. No. 6,660,007 assigned to the applicant also describes laminoplasty plates for open door and double door techniques with a spacer in the middle to maintain the decompressed lamina position. Different sized spacers are required depending on the extent of the laminar displacement required.
There is a need for a laminoplasty fixation implant that can also be placed through a minimally invasive approach with a variable size adjustable to the spinal anatomy of the patient. The present invention is an apparatus for use in either the open door or double door laminoplasty technique to stabilize the lamina in the spine thereby preserving the range of motion as well as maintaining stability. It also provides for a universal laminoplasty implant with a spacer that can be expanded or reduced in size depending on the patient anatomy and the degree of spinal canal decompression required.